linux-kernel - [PATCH 1/2] dma-mapping: remove bogus test for pfn_valid from dma_map

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Message-Id: <20210930013039.11260-2-rppt@kernel.org>
Date:   Thu, 30 Sep 2021 04:30:38 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Alex Bee <knaerzche@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Christoph Hellwig <hch@....de>,
        David Hildenbrand <david@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Mike Rapoport <rppt@...nel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Robin Murphy <robin.murphy@....com>,
        Will Deacon <will@...nel.org>, iommu@...ts.linux-foundation.org
Subject: [PATCH 1/2] dma-mapping: remove bogus test for pfn_valid from dma_map_resource

From: Mike Rapoport <rppt@...ux.ibm.com>

dma_map_resource() uses pfn_valid() to ensure the range is not RAM.
However, pfn_valid() only checks for availability of the memory map for a
PFN but it does not ensure that the PFN is actually backed by RAM.

As dma_map_resource() is the only method in DMA mapping APIs that has this
check, simply drop the pfn_valid() test from dma_map_resource().

Link: https://lore.kernel.org/all/20210824173741.GC623@arm.com/
Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
---
 kernel/dma/mapping.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 06fec5547e7c..dda8d8b84a55 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -296,10 +296,6 @@ dma_addr_t dma_map_resource(struct device *dev, phys_addr_t phys_addr,
 	if (WARN_ON_ONCE(!dev->dma_mask))
 		return DMA_MAPPING_ERROR;
 
-	/* Don't allow RAM to be mapped */
-	if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))
-		return DMA_MAPPING_ERROR;
-
 	if (dma_map_direct(dev, ops))
 		addr = dma_direct_map_resource(dev, phys_addr, size, dir, attrs);
 	else if (ops->map_resource)
-- 
2.28.0